overlays: sdhost: Add gpios_22_27 and bus_width parameters#7467
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pelwell
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Jul 2, 2026
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| debug Enable debug output (default off) | ||
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| bus_width MMC bus width (default 1) |
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The default bus-width is theoretically platform-dependent, but in practice it is always going to be 4.
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I've removed the bus_width parameter per your feedback and kept only gpios_22_27 . The commit has been updated with a proper description and Signed-off-by. Ready for review.
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Delete the README entry for the bus_width parameter, then I'll merge it. |
Add a new optional parameter to the sdhost overlay: - gpios_22_27: Routes the SD0 interface to GPIO 22-27 (CLK, CMD, DAT0-3) using ALT0 function, with appropriate pull configuration (CLK: no pull, CMD/DAT: pull-up). This allows custom CM4 carrier boards to use a secondary SD card slot wired to these pins. The parameter is implemented as dormant fragments and has no effect unless explicitly activated, preserving full backward compatibility with existing configurations. Tested on CM4 carrier board (EDATEC IPC2100) with: dtoverlay=sdhost,gpios_22_27=on,pio_limit=1 Signed-off-by: zjzhao <zjzhao@edatec.cn>
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Sorry, I forgot to update the README as well. I've now removed the bus_width parameter from both the DTS and the README. |
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Summary
Add
gpios_22_27andbus_widthparameters to the sdhost overlayto support CM4 custom carrier boards that route SD0 to GPIO 22-27.
Motivation
Some CM4 carrier boards (e.g. industrial IPC boards) wire a secondary
SD card slot to GPIO 22-27 rather than using eMMC. The stock sdhost
overlay provides no way to configure this pinmux, forcing users to
maintain separate out-of-tree overlays.
Changes
gpios_22_27override: activates fragments 3 and 4bus_widthoverride: exposes bus-width configurationTesting
Verified on CM4 + EDATEC IPC2100 carrier board:
config.txt used for testing:
dtoverlay=sdhost,gpios_22_27=on,bus_width=4,pio_limit=1